An integrated long range plan is presented to investigate seminiferous and epididymal tubule physiology. Permeability of the seminiferous tubules (blood testis barrier studies) and ductus epididymis to selected ions, organic molecules and steriod hormones will be defined. Intratubular hydrostatic pressure will be studied. Tubule fluid, osmolality, sodium and potassium concentration will be measured. Finally the mechanisms regulating the above parameters will be investigated. Micropuncture techniques developed to study renal physiology have already been adapted in our laboratory for use in these studies. The information derived from this work will have practical application in the clinical fields of male fertility control and infertility.